Impact wrench



April 14, 1959 Rs. SHORT v 2,881,885

IMPACT WRENCH I 4 Sheets-Sheet 1 v Filed Dec. 31, 1956' lll/l R s. SHORT 2,881,885

IMPACT WRENCH April 14, 1959 4 Sheng-sheet 2 Filed Dec. 31, 1956 R\S.\ SHORT IMPACT WRENCH April 14, 1 959` 4 Sheets-Shree?l 5 Filed Deo. 31, 1956 R s. SHORT IMPACT WRENCH April 14, 1959 4 4 Sheets-Sheet 4 Filed Dec. s1, 1956 NN. mwa@ UNWIN United States Patent O IlVIPACT WRENCH .R Stanford Short, Bryan, Ohio, assigner t The Aro Equipment Corporationfrygn, Ohio; a corporation of Ohio" Application December 31, 1,956, Serial No. 631,751

13 Claims. (C l. lill-30.5)

This invention relates to an impact wrench or similar type of impacting tool wherein rotary impact blows are delivered by an output end ofl the mechanism when a pneumatic motoror the like is connected with the input end thereofl and energized for rotating the mechanism.

@ne object of the invention is to provide a comparatively simple and rugged mechanism interposed between a source of power and the work, such as screwing a nut on a bolt, for initially rapidly rotating the work until a predetermined resistancev to torque has been builtup whereupon the mechanism operates to deliver a series of rotary impact blows to the worlr as long as the motor continues Ato operate. Conversely, as when loosening a nut, impact blows are first delivered until the nutis loose and then it is automaticallyy quickly rotated ottI the bolt when the resistance to torque reduces because of the nut being loosened.

The prime object of the invention is to provide a design in which multiple motor` revolutionsV are permitted. per impact b low and thus a harder impact blowI is produced by vincreasing the momentumof the mechanism.

Another object is toA provide a mechanism of inexpensive construction involving a minimum number of parts, and so designed as to require a minimum ofjtime and parts in replacement when the wear adv-ances to a stage requiring such replacement.

Another important object of `the invention is to provide an impacting mechanism having apower-driven member and an anvil, with a hammer interposed betweenl the two and so related thereto as to be clutchedV and declutched relativel tothe power-drivenV member and'` also relative to the anvil, the operation being suchA that the` hammer is sequentiallyy rotated by. thel power-driven. mechanism, then released therefrom, then clutched in relation to. the anvil fordeliveringV an. impact blow theretoA and iinally released from. the anvil and! re-engaged. withk the power-driven member during' a complete. cycle of impacting. operation, thus' permitting the. hammer member to rotatev as a free body prior to delivering the. impact blow.

Still' another object is toproyide. an impact clutchy construction in which an impacting element and; hammer driving elements of the` clutch are. mountedv within a hammer element for axial movement relativev thereto. and independently thereof: tcpermit clutching and declutching in relation to an anvil and in relation to a powerdriven member respectively whereby rotary impact momentum of all the elements together is imparted tov the anvil upon impact. Suchl hammer, impacting and driving elements are proportioned to provide a relatively rugged mechanism conducive to less wear than the usual type of impact clutch by positive disengagement of the impact element. from. the, anvil.' fase, following, imgaC-t- T11-US disengagement and relative. Sliding, meting. between the mpact element and the face. are permitted after the immer is dissipated. tc. tt1f.w.\' .zr1=.y and th. engaging Surfaces are. at. mimmlmi` unit pressure. distinguished imm other impacting mechanisme which declutch. during the impact Patented Apr. 14, 1959 ICC and therefore` during a time when high unit pressures. are involved. L' also provide extensive supporting and bearing surfaces for the impact and hammer driving elements throughout the major portions of their lengths which further contributes to` minimizing wear, and whereby the radial dimensions of the clutch are broughtwithinv relatively small limits for ease in handling and manipulation of the tool'.

A further object is to provide a mechanism wherein the hammer is released from the motor prior to impact so that the hammer and impacting member carried thereby strike a blow on the anvil as a free body, thereby eliminating the effects of the blow beingcarried back: through the mechanism and imparted to the motor which results in improving motor and bearing life and improving motor performance and elciency. f

Still a further object is Ito provide a positive. means of clutching and declutching the hammerl with respect to the anvil: controlled by the motor rotation! and in controlled time relationship with the anvil, thereby controlling the number of revolutionsA per impact blow.y

An additional object is-toprovid'e impacting mechanism in which the hammer member is releasedv from. the, powerdriven member to allow the motor driving the powerdriven member to recover speedjbefore the hammer is reengagedf therewith, thereby permit-ting more` rapid'. acceleration of the.l hammer uponre-engagement.

Another additional object is to provide impacting mechanism designed so that eccentricities of rotating members are minimized or eliminated, thereby reducing or eliminating shaking forces or vibration being set up in the mechanism which are uncomfortable to and/or uncontrollable by the operator and in which wear is minimized by the impacting member and the hammer driving members` are rotated to present a different strikingsurface each time. v

A further additional objectL isv to provide an impact clutch construction wherein the impacting element. is in the` form.. of a rod extendable through the end, portion of the hammer member and opposed to the anvil member; to engage and impart hammer blows on the. anvil member in the movement of the rod axially relative, toy the hammer and dependent on the position of the power-driven member Still a further additional object is to. provide an. impact clutch construction wherein the hammer driving element isin the form of ay rod whichv extends from anend of the hammer. member and engages or releases the, hammer in respect tothe motor driven member by means or axial movement of the rod relative to the hammer and independently thereof,` such movement being dependent on the position of the anvil member.

Constructionally, IA provide rotatable power-,driven hammer and' anvil members with pin-like hammer driving and impacting members slidable axially in the hammer memberI and controlled by cams on the anvil and power-.driven member respectively, the hammer driving members. being clutched and des-clutched relative. to the power-driven member bythe cam of the anvil andthe impacting. membeibeing clutched and declutched relativeto the anvil b y at cam groove of thelpower-driven member.

With these and other objects in View, my invention. cons ists in the. construction, arrangement andcombination of the various parts of my impact, wrench, whereby the objects above contemplated are attained, as hereinafter more fully set foi-,thx pointed out in my. claims and illustrated in detailon the accompanying drawings,` wherein:

Fig. l is, a vertical sectional view through an. impact wreneh embodying my present invention 'and showing the adjacent portion of a pneumatic motor on which it is, mounted;

Figs. 2 and 3 arevertical sectional'l views. on,e the lines A2--2and 3--3 respectively of Fig. 1, the impact wrench of Fig. 1 being taken on the line 1-1 of Fig. 2;

Fig. 4 is an exploded perspective view of the impacting mechanism, the 4housing therefor and the adapter for mounting `thehousing on a pneumatic motor, the' parts of a hammer assembly thereof being in assembled relation;

Fig. 5 is a further exploded perspective view of the positions of the parts during other portions of one complete impacting cycle;

' Fig.11 is a developed sectional view'of a cam groove for an impacting member and is formed in the periphery of a power-driven member of the impacting mechanism as taken on the line 11-11 of Fig. 2; and

Fig. 12 is a similar developed sectional view of a cam surface for a hammer driving member, this cam surface -being formed on an anvil as indicated by the line 12-12 of Fig. 3.

On the accompanying drawings I have used certain reference letters to indicate in general the main parts of my impact mechanism and a list thereof follows:

P--power-driven member H-hammer A-anvil I-impacting member D1-hamrner driving member DZ-hammer driving member There is also provided a housing for the foregoing parts. It has a ange 12 secured to an adapter 16 by cap screws 14 (see Figs. l and 4) and the adapter is mounted on a pneumatic motor housing or the like 18.

The stator of this motor is indicated at 20 and the rotor. thereof at 22, a vane type motor being illustrated and the vanes being indicated at 24. The rotor 22 has a shaft 26 which is splined as indicated at 28 to ntert with a splined bore 30 of the power-driven member P.

The hammer H has a central bore 32 which receives a bushing 34 for journalling the hammer H on the powerdriven member P. The mem-ber P is supported at its right-hand end in Fig. 1 on the rotor shaft 26 and at its left-hand end on a ball spacer 36 seated between this left-hand end and the anvil A. The ball 36 transmitsy thrust of the anvil A during operation of the tool through the member P to a ball bearing of the pneumatic motor. The anvil A has a shaft-like portion 38 journalled in a bushing 40 of a hub 41 on the housing 10. A grease seal `is provided at 39. Thrust surfaces 42 of the anvil and 440i the bushing are shown in engagement with each other. The shaft-like portion 38 terminates in a squared portion 46 to engage in a wrench socket or other tool to which rotary impact blows are to be imparted.

The hammer H also has a bore 48 to slidably and rotatably receive the impacting member I, and a pair of bores 50 to slidably and rotatably receive the hammer driving members D1 and D2. v The power-driven member P has a projection 53 provided with drive shoulders 52 and 54 for coaction with the hammer driving members D1 and D2. The shoulder S2 is for clockwise rotation and the shoulder 54 is for counterclockwise rotation. It also has a cam groove 56 that receives a flange 58 of the impacting member I for axially sliding this member in its bore 48 as will.`

vpact receiving shoulder 60 for cooperation with'the impacting member I when theimpact mechanism rotates counterclockwise. It also has a cam surface 64 to actuate the hammer driving members D1 and D2 by cooperation with heads 66 thereof. The cam surface 64 as shown in Fig. 12 is depressed relative to a land 65 of the anvil A. The heads 66 cooperate with the land 65 also so that 64 and 65 together are the controlling cam surface for the hammer driving members `during 360 of rotation.

The hammer driving members D1 and D2, as shown in Fig. 1, each comprisesa sleeve 68 in which a stem 70 of the head 66 is slidably mounted and limited in its sliding movement by opposed slots 72 of the sleeve and a pin 74 extending through the stem 70 and having its ends located in the slots 72. A cam follower spring 76 is provided under the head 66 to cause it to follow the cam surface 64--65 against the hammer H. A hammer driving member extension spring 78 is provided under the head 66 and seats againstthe end of the sleeve 68 to normally retain the pins 74 at the left end of the slots 72 and thus the sleeve 68 and the stem 70 extended relative to each other, yet permit their contraction in length as permitted by the pin and slot connection in case the driving members D1 and D2 strike the under face (lefthand face in Figs. 1 and 4) of the projection 53.

Practical operation.

Various positions of the parts during anv impacting cycle are illustrated in Figs. 6 to 10 inclusive. These gures are somewhat diagrammatic and the hammer driving members D1 and D2 are shown of simple one-piece construction instead of the telescoping sleeve and stem type illustrated in Fig. l as the telescoping construction does not enter into the impacting. operation except to prevent breakage of the parts in the event that the member D1 or D2 is driven by the cam surface 64 against the projection 53 when it is in a position of registry with respect to either D1 or D2. The telescoping connection permits the stem 70 to slide into the sleeve 68 opposed by the vspring 78 until the projection 53 has moved out of the way whereupon the spring 78 will expand for again telescoping the member D1 or D2 to its original length.

When a suitable socket or adapter (not shown) is associated with the squared portion 46 of the anvil A and such socket is applied to a nut, cap screw or the like for tightening it (clockwise rotation), the parts would be in the position of Fig. 6 at the instant of impact. The impacting member I is positioned axially by the cam groove 56 to engage with the impact receiving shoulder 62 of the projection 61 of the anvil A as shown in sec. F--F. Hammer driving member D2 is shown in a retracted position with respect to the projection 53 as permitted bythe cam surface 64 and as caused by the spring 76 as shown `in sec. A--B-D. This retraction of the driving member Dzis accomplished several degrees of Vrotation'prior to the positionof Fig. 6, thus disengaging the power-driven member P fromthe driving member D3 which releases the hammer'H. This permits the hammer to rotate momentarily as a free body untilA the impact member I that it carries delivers an impact blow to the 'impact receiving shoulder 62 of the anvil A. The driving member D1 is in an engaging position as shown in sec. A--B-C.

vH from the anvil A by retracting the impacting member I (secs. A-B-C and A--B--D). The position of all members except P and I remain the same as in Fig. 6.

In Fig. 8, the power-driven member P continues to rotate relative to the hammer H until the driving member D1 is engaged by the drive shoulder 52 as shown in sec. E-E. The cam groove 56 continues to hold the impacting member I retracted or disengaged relative to the anvil, During this rotation al1 members except the powerrtive to said" output element -for normally rotating said Aoutput element and for delivering impact blows thereto 6. In a rotary impact tool, 'an impact mechanism comprising apower-driven element, an anvil'element, a

hammer element to be driven by said power-driven velement and to rotate said anvil element and deliverimpact blows thereto, means for clutching said hammer element relative to said power-driven element and declutching it'relative to said anvil element to transmit Irotation from said powerdriven element to said hammer elementmeans responsive toV resistance to torque'for `declutching said hammer 'elementjfrom said power-driven element and clutchingit to said anvil element to deliver a rotational impact blow thereto, said means comprising I 'a hammer driving element, a cam on said anvil element 'for actuating'said hammer driving element, an impacting element, a cam on said power-driven element for actuating said impacting element, and said hammer driving and impacting elements being carried by said hammer Velement and movable relative thereto under the action of said respective cams.

7. In a vrotary impact tool, an impact mechanism comprising an input element, an output element and a hammer element located axially between said input element and said output element, said hammer element being adapted to be driven by said input element whereby to rotate said output element, and at times to impart impact blows thereto, a rst means axially slidable of said hammer element for clutching and declutchingy said hammer element relative to said input element, and separate second means axially slidable of said hammer element for clutching and declutching said hammer element relative to said output element, said Erst means having a projection and said output element having a cam coacting therewith to eiect axial sliding of said rst means relative to said hammer element, said second means having a projection and said input element having a cam coacting therewith to eiect axial sliding of said second means relative to said hammer element.

8. In a rotary impact tool, van impact mechanism comprising anv input element, an output element and a hammer element, said hammer element having an axially slidable element tobe driven by said input element and an axially slidable element to rotate said output element, and to impart impact blows thereto upon predetermined resistance to torque, means for clutching and declutching said rst slidable elements relative to said input element,

means for clutching anddeclutching said second slidable element relative to said output element, said iirst means being responsive to relative motion between said hammer element and said output element and said second means being responsive to relative motion between said hammer element and said input element, said rst slidable elementv being of spring extended, telescopic construction.

9. In a rotary impact tool, an impact mechanism comprising an input element, an output element and a hammer element, said hammer element having a iirst slidable element to be driven by said input element and having a second slidable element to rotate said output element and impart impact blows thereto upon predetermined resistance to torque, means for clutching and declutching said slidable elements relative to said input element and relative to said output element, said means being cam responsive, said output and input elements having cams for actuating said means, said first slidable element being of telescopic character, spring means to normally extend the same, and means to limit such extension.

f 10. In a rotary impact tool, an'impact mechanism comprising a power-driven element, an anvil element, a hammer element to be driven by said power-driven element rand to deliver 'impact Ablows to said'anvil element, rst means for clutching said hammer element relative to'said power-driven relement and declutching it relative 'to said anvil element to transmit rotation from said power-driven element to said hammer element, and separate second means responsive to resistance to torque for declutching said hammer element from said power-driven element and clutching it to said anvil element to deliver a rotational impact blow thereto, said rst means being 'carried by vsaid hammer element and being movable into and out of the path of said power-driven element only and Said second means, being carried by said hammer element and being movable into and out of the path of said anvil element only. n

l1, In a rotary impact tool, an impact mechanism comprising a power-driven element, an anvil element, a hammer element to be driven by said power-driven element and to deliver imp act blows to said anvil element, rst means for clutching said hammer element relative to said power-driven element and declutching it relative to said anvil element to transmit rotation from said power-driven element tol said hammer element, and second means responsive to resistance to torque for declutching said hammer element from said power-driven element andy clutching it to said anvil element to deliver. a rotational impact blow thereto, said rst means being carried by said'hammer element and being movable into and out of the path ,of said power-driven element and said second means nbeiiilgcarried by said hammer element and being movable into and out of the path of said anvil element and cams on said anvil and power-driven elements for actuating said irst and second means respectively. f

` 12. In a rotary impact tool, an impact mechanism comprising an input element, an output element and a hammer element, said'hammer element having a iirst movable element to be driven by said input element and having a second movable element to rotate said output -ele'ment and impart impact blows thereto upon predetermined resistance to torque, rst and second means for clutching and declutching said movable elements Irelative to saidy input element and relative to said output element, said second means being cam responsive, and said output and input elements having cams for actuating said means in response to resistance to torque.

13.In a rotary impact tool, anV impact mechanism comprising an input element, an output element, and an operative connection between the two comprising solely a'hammer element and rst, second and third declutching means carried by said hammer element, said hammer element being provided to be driven by said input element throughy said irst declutching means only in one direction andsaid second declutching means only in the opposite direction, and to drivesaid output element and deliver impact blows thereto through said third declutching means only, said rst or second means only clutching said hammerelement relative to said input element to transmit 'rotation' from said input element to said hammer element and for declutching said hammer element relative to said input element to permit said vhammer element to rotate as a free body,y said third means only clutching said hammer element relative to said output element for normally rotating said output element and for delivering impact blows thereto upon predetermined resistance to torque being encountered, and declutching said hammer element relative to said output element to permit reclutching of said hammer element relative to said input element by said first o1-'second means only depending upon the direction of rotation.

References Cited in the le of this patent 

